The Geology of Crater Lake National Park, Oregon With a reconnaissance of the Cascade Range southward to Mount Shasta by Howell Williams
The Glaciation of Mount Mazama
Evidence of Glaciation Outside the Caldera
The Castle Creek Glacier
The ice on the southwest slope of Mount Mazama entered the broad and deep canyon of Castle Creek and there joined the ice discharged from the north slope of Union Peak. In point of size, this was the largest of all the glaciers fed by Mount Mazama, for its total length was approximately 17 miles. Not only did it fill the canyon of Castle Creek, but it covered the entire ridge to the north with the exception of the topmost 100 feet or so of the cinder cone forming 6236 Hill. Even 5 miles west of the park boundary, the lava ridge on the north side of the canyon was under ice.